1991 Ford Mustang Idle Stall

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MISSISSIPPI MAN
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I have been having trouble lately w/ keeping the car running after it the engine has running for about 10-20 minutes. The first time this happened, the car did not want to idle. It would run as long it was kept revved up. But as soon as you let off the gas it would go dead. And when you drove it and got to a cruising speed, it would buck so hard it chirps the tires. I changed out the idle control valve and and udjusted the throttle up and it idlled just fine and ran great for about a week. Then the other day, i was coming down the off ramp of the interstate and the car died. I tried recranking it and it would not start. I left it on the side of the road most of the day and when i went back to get it, it started up fine and ran great for a couple more days. Then today at the same spot on the off ramp it started sputtering and wanted to go dead. I kept it revved as much as possible in order to make it to work. It started bucking again at cruising speed in every gear and wanted to go dead. This is aggravating me because i don't know where to start in fixing the problem. The motor is a rebuilt 302 to a 306. It has aftermarket heads, intake, throttle body, mass air and has roughly between 5-10,000 miles on it. The car has run great until the last few weeks. If anyone has a clue to what might be the problem, i'd very much appreciate an answer.
Dec 1, 2006 at 1:27 AM
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CATCH_15
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The first thing to do would be to run a fuel pressure test. It sounds like the fuel pump is weak and needs replacing. If that checks out though, since it is mass air, I would try replacing the MAF sensor.
Dec 1, 2006 at 3:44 AM
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MISSISSIPPI MAN
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I cranked it up today and it runs very roughly. Spitting and sputtering and blowing greyish black smoke. Will go dead as soon as i let off the throttle. I have a fuel pressure guage mounted in the car and it registers at ten pounds. Normally it is at 30 pounds. Is this a sign of the fuel pump going out or is it not registering right because it is running so roughly?

I changed the fuel filter while i was at it and is was fine but it did look like there were small metal shavings in the fuel that came out of it. Could these shavings be from a failing pump?
Dec 2, 2006 at 7:00 AM
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CATCH_15
  • ✓Experienced Mechanic
  • 250 POSTS
It sounds like the car is running rough because it's starving for fuel. Try replacing the fuel pump and that should make a world of difference.
Dec 2, 2006 at 7:14 AM

Suggested Repair

Replace the fuel pump. Fuel pressure is only about 10 psi instead of the normal 30 psi, and metal shavings in the fuel filter point to a failing pump starving the engine.

Conversation Summary

A 1991 Ford Mustang with a rebuilt 306 and mass-air setup dies at idle after warming up, bucks at cruise, and sometimes will not restart until it sits. Replacing the idle control valve only helped briefly. With a gauge showing about 10 psi instead of 30 and metal shavings in the fuel filter, the expert said the engine is starving for fuel and recommended replacing the fuel pump.

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